A housing of a portable electronic device, such as a mobile phone, a smartphone, or a laptop computer, is provided with an opening portion for maintaining ventilation between the inside and outside of the housing. The opening portion allows elimination of pressure difference caused by temperature difference between the inside and outside of the housing and also ensures sound transmission between the inside and outside of the housing in which an electroacoustic transducing part such as a microphone or a speaker is placed. It is becoming increasingly common to place a waterproof gas-permeable membrane over the opening portion to prevent entry of water into the housing. The waterproof gas-permeable membrane is typically a PTFE membrane made porous by stretching (stretched porous PTFE membrane).
A waterproof ventilation member is also known which includes a waterproof gas-permeable membrane and a fixing member which are preliminarily integrated together to increase the ease of attachment of the waterproof ventilation member to the opening portion. As the fixing member there is used, for example, a double-faced adhesive tape attached to an edge portion of a waterproof gas-permeable membrane (see, for example, Patent Literature 1, in which the tape is referred to as “double-faced bonding tape”). Patent Literature 1 discloses an assembly including: a pair of double-faced adhesive tapes so joined to a stretched porous PTFE membrane that the stretched porous PTFE membrane lies between the double-faced adhesive tapes; and an acoustic gasket joined to one of the double-faced adhesive tapes. A foam material such as a silicone foam is used as the material of the acoustic gasket.